Newhart was already an established television star and comedian before being brought on board The Big Bang Theory. Perhaps his most iconic roles were in the sitcoms The Bob Newhart Show and Newhart. The latter even had one of television's most lauded series finales.
Newhart has had several other television credits to his name since then. He briefly starred in the sitcom George and Leo, and has enjoyed small parts in a variety of shows ranging from Mad TV to ER.
In 2013, he added The Big Bang Theory to his long legacy. Newhart played a fictional character by the name of Professor Proton, who was idolized by the show's main characters. The show's creator, Chuck Lorre, offered him the role. Lorre wanted to work with Newhart for years prior to his Big Bang casting. But the two could never find the right project until the hit CBS sitcom.
Although Newhart was interested in the opportunity, the comic had two very important necessities before joining the Big Bang family.
"No. 1, my scenes had to be taped live. There's a tendency to pre-tape a lot of stuff and put a laugh track on it and you lose something. With Newhart, Lucy, Honeymooners, Mary Tyler Moore, and All in the Family it was always done in front of live audience. I always felt that the live audience gives it adrenaline. That's the only way I function," Newhart once told The Hollywood Reporter.
His second demand was that he wanted to be a recurring character. Lorre was more than willing to agree to both requests.
Newhart knew that Big Bang's audience might not have been too familiar with his work. He was going to be 83 by the time he'd first appear on the show. With such a long career behind him, Newhart was well aware that his mainstream popularity might have experienced a steep decline. He brought his worries to Lorre himself.
"I asked Chuck, the writers and our director if they were going to announce I'm in the show before the taping," Newhart said. "I was a little nervous that the live audience wouldn't recognize me and there would just be silence."
But Newhart soon discovered he had very little to worry about after the reception he received for his appearance.
"They said, 'We'll come up on you, and thankfully they recognized me; they applauded and stood up," Newhart said.
Despite the decades between Bob Newhart and Big Bang, Newhart shared that shooting the two comedies had some comforting similarities.
"It's amazing how close the set resembled Stage 17 at Radford, where we did The Bob Newhart Show and Newhart. It was like going back in time. It was a relief," he said.
But those similarities still paled to the differences between the two shows. Newhart felt that more time was given to writing jokes in his own 1972 sitcom than in Big Bang. He believed that the change had a lot to do with the demographics that each show was targeting.
"When I was doing The Bob Newhart Show with [Suzanne Pleshette], we did a [scene] with an IQ test. It had to take a minute and a half to set up [the joke]" Newhart once told USA Today. "You don't have that kind of time today. You've got 15 seconds, and then bang! You'd better have another line. That's the dictates of the young audience. They want it and they want it now."